Underwater wireless optical communication using an arrayed transmitter/receiver and optical superimposition-based...

Area of Science:

• Optical Engineering
• Wireless Communication
• Photonics

Background:

• Underwater wireless optical communication (UWOC) systems face challenges with alignment, LED nonlinearities, and signal attenuation.
• Existing systems require precise alignment and are susceptible to environmental factors like turbidity.

Purpose of the Study:

• To propose and validate a novel UWOC system utilizing an arrayed transmitter/receiver with optical superimposition-based Pulse Amplitude Modulation with 4 levels (PAM-4).
• To enhance tolerance to LED modulation nonlinearities and relax alignment requirements for robust underwater communication.

Main Methods:

• A spatial summing scheme using a two-group interleaved LED array was designed for optical superimposition-based PAM-4.
• Monte Carlo simulations were performed to investigate system performance in various underwater channel conditions.
• A proof-of-concept experiment utilized blue LEDs and a multi-pixel photon counter (MPPC) detector.

Main Results:

• The spatial summing scheme demonstrated uniform optical power distribution, significantly relaxing link alignment needs.
• Data rates of up to 12.288 Mb/s were achieved over a 2-m tap water channel with a 2.5-MHz bandwidth.
• A bit error rate (BER) below the forward error correction (FEC) limit was recorded, indicating high power efficiency and robustness.

Conclusions:

• The proposed UWOC system effectively uses optical superimposition-based PAM-4 for enhanced communication.
• The integration of an arrayed transmitter/receiver and a high-sensitivity MPPC detector offers superior power efficiency and robustness.
• This approach significantly improves the feasibility of reliable UWOC systems in challenging underwater environments.